In conventional electrolysis cells having separate anode and cathode compartments, the anode, intervening separator and cathode are spaced apart from each other to allow for gas release and electrolyte circulation. In order to reduce the cell voltage, it has already been proposed to bring the electrodes into contact with the separator to form a narrow gap cell. Thus, in such a narrow gap electrolysis cell the passage of current from one electrode to an opposite electrode takes place only through the ionically-permeable separator which typically will be an ionic selective and ionic conductive membrane. Current flows from the surface of one separator to the surface of the separator of an adjoining cell only by electronic conductivity (i.e. via the current-feeder grids and their associated connections or bipolar separators), then flows ionically to the opposite surface of the separator.
However, problems have been encountered with these narrow gap cells, such as the loss of active electrode surface due to masking by the separator and the consequent need for large quantities of particulate electrocatalytic material to make up an effective electrode. When it is desired to use platinum-group metals or platinum-group metal oxides as the active material, the cost of these electrodes becomes prohibitive. Consequently, conventional membrane and diaphragm electrolysis cells with electrodes spaced from the separator still remain competitive despite their voltage penalty.
The state-of-the-art relating to narrow gap electrolysis cells is illustrated by the following U.S. Patents:
U.S. Pat. No. 3,870,616 PA1 U.S. Pat. No. 4,056,452 PA1 U.S. Pat. No. 4,191,618 PA1 U.S. Pat. No. 4,210,512 PA1 U.S. Pat. No. 4,214,969 PA1 U.S. Pat. No. 4,236,993 PA1 U.S. Pat. No. 4,253,922 PA1 U.S. Pat. No. 3,992,271 PA1 U.S. Pat. No. 4,057,479 PA1 U.S. Pat. No. 4,209,368 PA1 U.S. Pat. No. 4,212,714 PA1 U.S. Pat. No. 4,217,401 PA1 U.S. Pat. No. 4,247,376 PA1 U.S. Pat. No. 4,253,924 PA1 U.S. Pat. No. 4,039,409 PA1 U.S. Pat. No. 4,177,118 PA1 U.S. Pat. No. 4,210,501 PA1 U.S. Pat. No. 4,224,121 PA1 U.S. Pat. No. 4,250,013 PA1 U.S. Pat. No. 4,293,394
Examples of the particulate electrocatalysts that have been proposed for narrow gap electrolysis cells are: